THE STRUCTURAL BASIS OF CORTICAL SYNCHRONIZATION. I. THREE TYPES OF
INTERHEMISPHERIC COUPLING.
NOWAK, L.G., MUNK, M.H.J., NELSON, J.I., JAMES, A.C., BULLIER J.
Cerveau et Vision, INSERM Unit[acute]e 371, 18 avenue du Doyen
L[acute]epine, 69500 Bron/Lyon France, t[acute]el: (33) 72 13 15 83, fax: (33)
72 13 15 99.
APStracts 2:0259N, 1995.
SUMMARY AND CONCLUSIONS
1. Single and multiunit activities were recorded at the area 17/18 border of
each cortical hemispheres in paralyzed cats anaesthetized with nitrous oxide
supplemented with halothane. Cross-correlation histograms (CCHs) were computed
between 86 pairs of single units and 99 pairs of multiunit activities.
Visually-evoked peaks in the CCHs were removed by subtracting the shift
predictor. 2. Three types of CCH peaks were observed : T peaks with narrow
width (4-28 ms), C peaks with intermediate width (30-100 ms) and H peaks with
large width (100-1000 ms). 0scillatory coupling was observed rarely. This
tripartite distribution of CCH peaks is similar to that reported in an earlier
study on the temporal coupling between areas 17 and 18. Different types of
peaks occured in isolation or in combination. Combination of different peak
types was more often observed in multiunit recordings. 3. CCH peaks of all
types were usually centered, meaning that units in opposite hemispheres tend
to synchronize their discharges. 4. T peaks were observed almost exclusively
for units with overlapping receptive fields and preferentially for units with
similar optimal orientations. No dependence on receptive field position or
optimal orientation was observed for the encounter rate of C and H peaks. 5. A
new method, called the peri-stimulus cross correlation histogram, was
developed to study the time course of the temporal coupling. This showed that
H peaks can occur during visual stimulation and that their time course follows
that of the visual responses of the coupled neurons. 6. By using one single
bar or two simultaneously presented light bars as stimuli, we studied the
effect of visual stimulation on the strength of H coupling. This showed that H
coupling observed under stimulation with a single moving light bar can be
completely abolished, with little change in visual responses, when the
stimulus is changed to two non-coherently moving bars. This was related to a
strong decrease of the H peaks in the autocorrelograms. 7. These results
demonstrate that T, C and H peaks constitute, together with high frequency
oscillations, universal forms of temporal coupling between neurons located in
different cortical areas. The following paper reports on the effects of
cortical lesions on the encounter rate and strength of these different types
of coupling.
Received 12 May 1995; accepted in final form 27 July 1995.
APS Manuscript Number J257-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 15 September 1995.